Wireless propagation models are a group of mathematical expressions, charts or algorithms for predicting radio propagation characteristics in a given environment. A propagation model may be either an empirical model (also referred to as a statistic model) or a theoretical model (also referred to as a deterministic model), or a combination of both. The empirical model has high calculation efficiency but low calculation accuracy, and thus is often used for wireless signal prediction of a large outdoor scene. The theoretical model has high calculation accuracy but low calculation efficiency, and thus is often used for wireless signal prediction of an indoor scene.
With wide applications of mobile Internet services, mobile data traffic presents an explosive growth. According to investigation of the Japanese DoCoMo company, 80% of mobile data services occur indoors, establishment of indoor wireless networks has become the key that mobile operators satisfy the demand of mobile data services and improve users' satisfaction, so that a large number of indoor coverage networks in various of forms such as indoor distributed systems, repeaters, remote base stations, mini base stations and the like are born at the right moment, and these indoor coverage networks and an outdoor macro base station collectively form a seamless mobile communication network. However, while the establishment of indoor coverage networks satisfies the demand of indoor services, it also brings a series of problems among which the most prominent one is that interference between indoor and outdoor networks becomes increasingly serious, including leakage of an indoor signal to the outdoor, and interference of an outdoor base station signal to the indoor. In order to solve interference between indoor and outdoor networks, indoor and outdoor united networks planning and optimization has become the key point of future network planning and establishment by the mobile operators. Indoor and outdoor united simulation is the premise of indoor and outdoor united planning, while an indoor and outdoor united propagation model algorithm is the premise of performing the indoor and outdoor united simulation. However, there are mainly two types of wireless propagation models in the current industry, one of which is suitable for accurate simulation of a small indoor scene, and the other one is suitable for rough simulation of a large outdoor scene. Document [1] provides an outdoor-to-indoor propagation model, for which a ray tracing propagation model algorithm is adopted for the outdoor, and a time domain finite difference propagation model is adopted for the indoor. A deterministic propagation model is adopted for both the indoor and outdoor, which needs a large amount of calculation and has a low engineering availability. There is an absence of an efficient propagation model that can be applied for both indoor and outdoor united scenes.
In general, at present one technical problem that needs to be solved urgently by persons skilled in the art is to seek for a rapid and efficient outdoor-to-indoor propagation model algorithm to rapidly and accurately predict signal field strength generated in the outdoor-to-indoor three-dimensional space.